Several mobile machines, especially those used in forestry applications such as, e.g., forwarders, skidders, or feller bunchers, have a cab structure to protect the operator that includes a roll over protection structure (ROPS). For example, Frett et al. disclose a work vehicle including a typical operator cab frame and a roll-over protective structure mounted to the frame (published U.S. Patent Application No. 2008/0048426). Also, International ROPS Standards, such as ISO3471, SAEJ1040, AS2294.2, require that the operator cab withstand given lateral, vertical and longitudinal forces, as well as absorb a minimum lateral energy. In a machine roll over, the energy absorbing criteria assists in slowing down the lateral rotation of the machine. For conventional construction machinery ROPS, generally a rectangular tubular frame may absorb lateral energy by bending at the corners, in the manner of a parallelogram, without intruding into a defined operator space or coming up against the machine chassis.
Further, mobile machines that are used in a setting where they are often in physical contact with the environment, such as forestry settings, utilize polycarbonate windows to prevent damage to the windows and the operator. To accommodate both the ROPS and the use of polycarbonate windows, many machines have thick corner posts that may obstruct the operator's view and a polycarbonate window that is bolted into a frame through the window's periphery.
In the past, a machine's ROPS was the primary focus of the design, and thick, wide posts were incorporated in the ROPS. However, as different materials and different post substructures have developed, such as multi-walled tubes or waved shaped supporting post substructures, the material required to be used in a suitable ROPS post has decreased. Such a transition has also been motivated, in part, by the desire to increase operator visibility.
Another way that operator visibility was hampered in the past was the presence of a distinct ROPS post and a window frame. The window frame was commonly joined to the ROPS post or frame, then the windows were inserted to the frame and fastened in place, such as with a bolt through the window's periphery and into the frame when an outer plate was used to effectively sandwich the glass between the outer plate and the window frame. Overall, this additional structure further decreased operator visibility.
The present invention is directed to overcome one or more of the problems as set forth above.